The biplanar thyristor: A method for combining reliability and low costs

The "blocking" junctions of thyristors such as Silicon Controlled Rectifiers and Triacs having voltaire ratings ≥ 200v are normally fabricated by diffusing a P-type dopant from both top and bottom surfaces of a high resistivity N-type substrate. This approach provides the wide "N base" region which is necessary for adequate depletion from either junction at high voltages. Currently, either mesa or planar technologies are used. This paper introduces the biplanar® technology as a third and in many ways more attractive method for fabricating the two high-voltage junctions. The method of forming other junctions in a thyristor is identical in all three technologies and so will not be discussed.